Objective    To prepare monoclonal antibodies (mAbs) against preS1 to detect large surface protein (LHBs) in the serum of HBV carriers and investigate its clinical value.     Methods    According to the frequency of E. coli codons

an E. coli favorite DNA fragment

encoding amino acids sequence identical to that of the wild type preS1 (1 to 119 aa)（genetypeB

serotype adr） was cloned into plasmid pET32a. The preS1 protein was induced to express and then purified by cation exchange

His-tag affinity column

and then d

igested by enterokinase before it was used to screen its monoclonal antibody. LHBs preS1 B cell epitope peptide (36 to 58 aa) was forecast with aid of bioinformatics analysis softwares. Then the peptide was synthesized and then cross-linked with BSA. BALB/c mice were immunized with this cross-linked peptide through a new immunization procedure to produce mAb against preS1. An ELISA method was established to detect LHBs in the serum with these mAbs in blood serum samples of 413 identified hepatitis patients and 100 health individuals

and the results were compared with those of other commercial detection method.     Results    Highly purified preS1 (HPLC indicated a purity of 98%) was obtained. Our renewed immunization generated mAb (1-E6) (IgG

1

subclass) against preS1 with good specificity. The positive rate of preS1 was higher when our mAbs 1-E6 was used than other commercial mAbs was in detection of LHBs with ELISA (83.3% vs 72.9%

P0.01).      Conclusion    We obtain preS1 protein with high purity and suitable as standard substance

and efficient and specific mAb (1-E6) in detection of LHBs with ELISA.